1. Field of the Invention
The present invention relates to a plasma processing apparatus for processing a substrate sample such as a semiconductor wafer placed in a process chamber within a vacuum vessel by a plasma formed in the process chamber. The present invention also relates to a diagnosis method of a plasma processing apparatus for diagnosing the operation of a flow-rate controller that controls the flow rate of a process gas supplied to the process chamber of the plasma processing apparatus.
2. Description of the Related Art
A plasma processing apparatus has been widely used for forming the structure of a device circuit by applying a desired process to a substrate sample such as a silicon semiconductor wafer or an LCD substrate in the process of manufacturing semiconductor devices. The plasma processing apparatus forms a plasma by exciting a process gas of one or a plurality of types of gases introduced into a process chamber placed in a vacuum vessel by the electric field or magnetic field supplied to the process chamber. Then, the plasma processing apparatus performs etching or other processes by using charged particles such as ions and highly reactive particles in the plasma.
In the process of the plasma processing apparatus described above, it is necessary to stabilize the flow rate of a plurality of process gases to be introduced, and to reproducibly supply the process gases. In recent years, the types of process gases used for manufacturing semiconductor devices as well as the conditions used for processing the flow rate and the like have been diversified. In these circumstances, it is required to achieve the conditions of a wide range of flow rates from large to small flow rates in one process chamber to process the sample. For this reason, the process gases of a wide range of flow rates (speeds) are supplied by using a flow-rate controller of one type and configuration.
In such apparatus, it is necessary to detect a very small value of the flow rate of the process gas, in order to stably and reproducibly achieve the small value of the flow rate of the process gas. Thus, there has been developed a process gas flow-rate controller for plasma processing apparatus including a manometer that can detect the range of low gas pressure with high accuracy, or including a flow-rate detector that can detect small flow rate with high accuracy.
An example of the related art is a semiconductor manufacturing apparatus including a mass-flow-rate controller and an opening/closing valve in a fluid feed passage with an exhaust device provided in an end thereof, which is for example described in Japanese Unexamined Patent Application Publication No. 2007-214406. The semiconductor manufacturing apparatus has a controller for controlling the operation of the mass-flow-rate controller, the opening/closing valve, the exhaust device, and the like. Then, the mass-flow-rate controller has a testing function and/or a flow-rate correction function for flow rate control.